Screw-propeller.



G. STEIGBR.

SCREW PROPEI LER. APPLYIOATION FILED K0128, 1905.

Patented Nov. 24, 1908.

I \N\/ ENTER. CARLSTEIGER wwm: szs

vex and a concave curve.

CARL STEIGER, or BENDLIKON, NEAR ZURICH, SWITZERLAND.

SCREW-PROPELLER.

Specification of Letters Patent.

Patented. Nov. 24, 1908.

Application filed November 28, 1905. Serial No. 289,385.

To all whom it may concern:

Be it known that I, CARL STEIGER, a citizen of Switzerland, residing andhaving a post-oflice address at Bendlikon, near Zurich, in the canton ofZurich, Republic of Switzerland, have invented certain new and usefulImprovements in and Propellers; and I do hereb Y declare the followingto be a full, clear, and exact description of the invention, such aswill enable others skilled in the art to which it appertains to make anduse the same, reference being had to the accompanying drawings, and toletters of reference marked thereon, which form a. part of thisspecification.

This invention relates to screw propellers, the object being to providea propeller of increased efficiency as compared with propellers hithertoin use, and one by which vibration is greatly reduced.

Each section of a propeller-blade, situated on a cylinder concentric tothe propeller shaft, must have a certain thickness in proportion to itslength. The more distant from the propeller shaft such a section issituated, the less may be this thickness. The question 1s, now, to find,for a certain strength of blade, the most favorable forms of thesections. The plurality of the propellers now in use are plane on theactive or rear side of the blades and more or less convex on the frontside.

By trials, carried out by the inventor, as well with floats in the wateraswith propellers on ships, it has been found that the etficiency of apropeller becomes ,better, if the rear sides of said sections arecomposed of a con- But the proportion of the convex part to the concavepart shall .not be the same in all sections, but smallest about midwaybetween the base and the point of the blade, while this proportionincreases with the sections towards the base of the blade and towardsthe top of the blade. This result was found by trials, and forms theessential feature of the invention. It arises partly from the fact,that, in this form of section, the front side is less convex, as it werethe case, in sections of the same area but with plane rear sides, andwhereby -great cavitations were produced.

Referring to the accompanying drawing: Figure 1 shows, in aside-elevation, one form of construction of a blade constructedaccording to the present invention.

Relating to Screw- Fig. 2 wards the back. Screw shows three of thesecylindrical sections, a, b, with such blades have,

a, concentric to the propeller shaft on the line A A., B-B, CC in Fig.l, 2'. c. the horizontal parts of these lines indicate the foremost andhindmost points of the section. The curved portions of the linesindicate the projections of the inter-section lines between thecorresponding section cylinders and the parts of the upper surface ofthe blade visible in these projections.

In the figures, the left side is the side of the propeller which isnearer the ship. The forward movement of the ship is effected when thepropeller is rotated in an anticlockwise direction as viewed from therear. The back of the blade is, therefore, the working side. As may beseen from F ig. 2, on the working side, each of the cylindrical bladesections is bounded by a curve which consists of a concave and a convexpart. The proportions, in length, between both these parts in thevarious sections is also various. Whereas in the section 0 the convexpart considerably exceeds the concave part, in section 7), however, theformer forms only a small fractional part of the latter. In section a,the relation is again almost the same as in section 0. Section I) isdistant from the base of the blade at about of the distance between thisbase and the top of the blade. this section may be situated a littlewithout or within or at the middle of said distance, without departingfrom the spirit of this. invention. The curve DD, in Fig. 2, connectsall the points in which the concave parts of the boundary lines of thevarious sections pass over into the convex. The greatest thickness ofeach working blade cross-section is in its front third part, differingfrom the most screw blades in use up to the present, where the greatestthickness is in the middle of the breadth of the blade.

Experiments carried out by the inventor with floats in water haveresulted, that with a certain strength of blade toward the front edgethe blade action is not only better than when the. greatest strength ofthe blade is situated in the middle of 'the breadth of the blade, but ismore favorable than with a blade, which consists of only a uniformlythin sheet, furthermore that it is advantageous to allow the ends of thefront and the back to meet at about a right angle. The blades should beas pointed as possible topropellers provided according to trials It willbe understood, however, that.

nade by the inventor, the advantage, as

and sizes of ships and can also be used onships running wlth high speedand as dragscrews.

What I claim is:

A screw propeller, in which the several cross sections of each bladeconcentric to the propeller axis are each composed of a concave and aconvex curve at the rear side of the blade, the proportion of the convex15 part to the concave part being smallest about midway between the baseand the point of each blade and increasing towards the base of the bladeand towards its point.

In testimony whereof, I have signed my 20 name to this specification inthe presence of two subscribing witnesses.

v CARL STEIGER.

Witnesses:

HERMANN' OUBER, A. LIEBERKNECHT.

